A waterfall that famously “disappears” into a hole at Judge C.R. Magney State Park near Grand Marais actually soon re-enters the river from underground, according to new research.

In fall 2016, hydrologists from the Minnesota Department of Natural Resources found nearly identical volumes of water flowing both above the Devil’s Kettle waterfall and below it. Above the waterfall, stream gauges measured the flow of the Brule River at 123 cubic feet per second. Below the waterfall, gauges detected 121 feet per second.

“In the world of stream gauging, those two numbers are essentially the same and are within the tolerances of the equipment,” explained DNR springshed mapping hydrologist Jeff Green. “The readings show no loss of water below the kettle, so it confirms the water is resurging in the stream below it.”

Green and Calvin Alexander, a colleague at the University of Minnesota, plan to conduct a dye trace to show where the water resurfaces. In the fall of 2017, during low-water flow, they will pour a fluorescent, biodegradable dye into the pothole and note where the dye re-enters the river.